Potential Analytical Methods for Stability Testing of Biodiesel and Biodiesel Blends

A literature evaluation of potential oxidative and thermal stability test methods for biodiesel and biodiesel blends with petrodiesel, as well as the known effects of stability related issues on performance in the field, has been completed. The advantages and disadvantages of the selected potential test methods were compiled to form a basis for further consideration and rating of the test methods. The literature search and rankings were peer reviewed by experts in the oleochemical, petroleum diesel, and diesel engine manufacturing fields. Based on the peer-reviewed rankings, limited bench scale testing was performed on selected test methods and various modifications to determine their applicability to biodiesel and biodiesel blends. For various reasons, none of the methods (as written) appeared to be reliable indicators of performance with biodiesel or its blends.

Modifications of ASTM 2274 (Accelerated Method), the ASTM 150°C high-temperature stability test (commonly referred to as the duPont F-21 or Thermal Stability), and ASTM D 4625 (43°C Long Term Storage) test methods were identified that may enhance their ability to accurately and reliably predict the performance of biodiesel and biodiesel blends. A working group was formed within the biodiesel task force of ASTM to further evaluate biodiesel stability testing methods. The information developed from this effort will be summarized in an appendix of the ASTM standard for biodiesel (currently a provisional standard), which is similar to that contained in the ASTM petroleum diesel fuel standard, ASTM D 975.